This invention relates to arrangements for automatically opening a door, hood trunk lid or the like for a motor vehicle. Such components to be opened automatically are usually motor vehicle trunk lids or rear liftgates that swing upwardly and are referred hereinafter as "doors".
In addition to arrangements which permit opening of a vehicle door by the manual application of opening forces, arrangements are also known which relieve human beings of the need to apply door opening forces and use motors for this purpose. One example of this type is disclosed in German Offenlegungschrift No. 40 40 372, in which a trunk lid can be opened and closed by a vehicle occupant from inside the vehicle by turning on a motor. Disadvantages of this arrangement include a relatively large energy expenditure, since the motor clearly must accomplish the entire opening motion of the door, and also the fact that it is not possible to open the trunk lid from outside the vehicle in this manner.
The latter disadvantage is avoided by an arrangement described in German Gebrauchsmuster No. 296 23 461, which includes a portable remote control unit for initiating unlocking and opening of a door. That arrangement is said to be useful in general for controlling the unlocking and/or opening of any device for opening a component of a motor vehicle, but it is not clear from the document what form the device for generating the opening forces should take.
U.S. Pat. No. 5,369,911 describes a motor vehicle door which can be unlocked by a wireless transmitter for actuating an ejector which is constantly kept under spring pressure. Once the vehicle door is unlocked by receipt of a transmitted signal, the ejector is driven by the spring to push the door into an open position.
This arrangement is disadvantageous because the ejector also exerts a relatively large torque on the door in the opening direction when the door is in its latched position. That torque must be absorbed by the latch, with the result that the unlocking force must overcome relatively large frictional forces in the latch.